Some existing systems provide users with accessibility or ease of access to a computer using various input methods. For example, some of the existing systems include a camera and face tracking algorithms. The algorithms identify facial features such as the eyes, nose, and mouth of a user. The eyes, for example, may be identified by flashing infrared light at the user to locate the retina. The tip of the nose may be identified by calculating the curvature of the nose. The orientation of a head may be determined by computing a mathematical normal of the face, or by using two cameras to generate a three-dimensional model of the face.
Such existing systems, however, either require expensive and dedicated hardware or require intensive computation not practical for real-time or near real-time use.